1. Field of the Invention
The present invention is directed to radio communication, and more particularly, to power control in a receiver having a low noise amplifier (LNA) with an adjustable gain which is controlled by a closed loop automatic gain control (AGC).
2. Discussion of the Prior Art
Several different modulation schemes are used for wireless mobile phones. One modulation method is the code division multiple access (CDMA) scheme where signals are broadband and occupy several channels. This is in contrast to the frequency division multiple access (FDMA) scheme where signals are narrowband and occupy one channel at a time. For optimal performance in wireless phones using CDMA, the power level of transmitted signals within the channels must be carefully controlled.
In a CDMA network, an induced interference, e.g. from other competing networks such as from the Advanced Mobile Phone Service (AMPS), has been recognized to have an adverse effect on the voice quality. Theoretically this interference can be minimized by allocating to each operator a dedicated spectrum. However, a mobile station (MS) experiences the competitor induced interference when the MS comes within a close vicinity of the competitor base station. This degrades performance and even causes a drop call where a call is lost.
Although, the competitor's interference resides on different spectrum, the nonlinearity in the receiver's components, e.g. the low noise amplifier (LNA), causes intermodulation, referred to as MIM, which is a source of co-channel and adjacent channel interference. The major source of MIM is the LNA. The present invention is related to a technique which minimize co-channel interference and hence increases the performance of the receiver.